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Why are car windshields laminated?

Side and rear windows are tempered so that they shatter into relatively harmless chunks on impact. But windshields are laminated, so that even though they shatter, all of the pieces are kept in place. Why is this? It seems that if a laminated windshield shatters/spiderwebs and remains in place, it would completely obscure the driver's vision while he is trying to control the car. Additionally, if someone is thrown from the car, through the windshield, they would be cut by the glass shards that are stuck to the laminate. So why are windshields laminated, or more importantly, why aren't all windows in a car made of the same type of glass?

I'm from NZ and until about the mid 80s most cars had tempered glass windscreen. tempered glass is much stronger and some ways a better material for a windscreen, but unfortunately when it breaks it fails catastrophically and is very difficulty so see through and scars the crap out of the driver, this can lead to an accident. Also some modern cars the windscreen it part of the structure of the car so a broken screen can make undriveable as you can see through it and you could damage the frame of the vehicle if driven. a laminated screen does not have these problems.
Kiteman1 year ago
The front windscreen gets the most impacts (stone chips, birds, pedestrians) so it needs to be strongest. The starring is far more preferable to thinfs actually coming through at highway speeds.

I've never heard of being thrown out the front window that was wearinga seat belt.
The only way to be thrown out the front window with a seat belt is if your body is bifurcated by the seat belt - at which point being ejected is the least of your worries.

The structural integrity of the windshield is MUCH more important these days because of the front passenger airbags that actually inflate upwards before outwards, filling the entire front cavity of the car to protect from going out the windshield. If the glass gives way, the airbag goes outside the vehicle instead of inside, and doesn't offer any protection.

http://youtu.be/aPQNQ6vgYn8?t=17s

At 17 seconds onwards you can see how the passenger airbag fills the whole front cabin.

@author "spiderwebs obscure the view" -- Once you've been in an impact hard enough to break your windshield, you no longer need to drive evasively, you need to be hard on the brakes and come to a complete stop. If the glass broke out, your eyes would be full of safety tempered glass shards (still sharp) and you couldn't see anyway.
I've seen people ejected with the seat belts still buckled. I've seen seatbelts fail and fully extend. I've seen seatbelts that have snapped.
Nothing is impossible -- but how old were those vehicles?
At the time (times) about 3 to 5 years. The most recent (snapped belt) occurrence about 4 or 5 years ago. So as of today, about 10 years. As you say, nothing is impossible, and anything can happen in a motor vehicle accident.
Re: @author "spiderwebs obscure the view" -- Once you've been in an impact hard enough to break your windshield, you no longer need to drive evasively ...

That's not the case. A small stone that got airborne by the tyre of the care in front of you will hit your wind screen with enough momentum (its own and the speed of your car combined!) to chip the glass. Would the glass be tempered like the side, it would "spiderweb" instantly, obscuring the view. With laminated glass, you get a chip on the outer layer that can be treated with some kind of transparent epoxy.

Your remark about structural integrity is correct. While a side windows is designed to be opened and therefore can bear no load, the wind screen is part of the static design of the passenger cell and stabilizes the car even while normal driving.
Windscreen are laminated because

a) they are very likely hit by stones or debris that somehow gets in the way of your car and should not 'spiderweb' as this would be unsafe due to the reduced view and expensive as the windscreen would have to be replaced (and some of them are 1500$ and up, ouch...)

b) they are part of the static design of the passenger safety cell. So they have to withstand some torsion forces that would shatter tempered glass.

A laminated glass will have a small spiderweb if it really should get a heavy impact by a big stone, but the other parts stay (somehow) intact. If the impact is on the passenger side, you should be able to see enough to stop the car safely. If the impact is on the driver side ... well, you would probably too shocked to do anything reasonable or be able to lean over to the passengers side.

Why not all glass is laminated? Well that stuff is strong, but heavy and expensive. And, with tempered sides, a quick hit will break the glass to give access from a rescue team to reach inside or a passenger to crawl outside. Armoured cars have all side laminated glass, but with more than two layers.

If you really get outside a car in a crash, you're an idiot for not wearing a seatbelt. Why do some people think it would be safer outside? First you go through the windscreen and then there is all the debris from the crash, including your own car, ready to roll over you!

Anyway, the shards from the laminated glass are still glued to the glass, not able to give you deep dangerous cuts.


Great answer. I was going to write something similar.
My late brother in law died being ejected during a rollover. He never wore his belt because (his flawed logic) "he would have been killed if he had not been ejected in the first accident based on the damage to where he was sat...he survived the FIRST ROLLOVER EJECTION so therefore its safer to be ejected"

...He got lucky once, and it killed him the second time.
Sadly the laws of probability and physics don't follow his flawed logic.

**Agreed with all of the above
JamesRPatrick (author)  frollard1 year ago
Let's stay on topic, people.
That was on topic...a comprehensive safety system is important in todays vehicles. I was adding some empirical evidence...doesn't matter how good your windshield and airbags are if you don't wear a belt :D
JamesRPatrick (author)  verence1 year ago
So this doesn't obscure the view?
A-g_WmcCYAIntTO.jpg
JamesRPatrick (author)  JamesRPatrick1 year ago
BTW this is from an object hitting the windshield only, not from a front- or rear-end impact.
no view= better than being blinded by flying shards of glass (in your eyes).
+1 Once the windshield is like in the picture, the vehicle is no longer drivable until the windshield is repaired. Vehicles with damaged windshields must be towed for repair.
I mean if you get in an impact hard enough to break the windshiled, it's gonna completely spider, not a just a little, and if it was an impact hard enough to obscure the view, it's an impact you're not going to correct your course by evasive action after that point. I did misuse tempered and laminated, slip of the brain.

Agreed, SMALL chips are great that they can be fixed, but having a breakaway windshield for the purpose of visibility after it's broken is a safety nightmare.
Addendum, watch at 1:10 and see how the safety glass all goes airborne in the side impact.

If that was a front rear end impact, it will cover the driver with broken glass at high speed.
Err, no.

The shards are flying away from the driver, outside as they don't change there momentum as fast as the car and/or driver. So, in a real crash they would stay fast while car and driver decelerate.

again, brain fart typo --

REAR END impact, if you get rear ended and your windshield broke under the stress (not uncommon, especially if it was tempered) -- , the windshield would have v=0,. the driver would be pushed forward into the stationary broken flying glass.
Front windscreens can only come inside the car if they or the car are effectively destroyed - they are fitted from the outside and the car frame is smaller than the glass.

Having been several accidents over the years, as passenger and as driver, in a rear-end shunt, the only things that have hit me were already loose in the car.
hypothetical, if it was made of tempered glass, not laminated glass. A rear end accident would/could shatter the front windshield of the front car and cover the driver in glass.
Ah, I see.
JamesRPatrick (author)  Kiteman1 year ago
Seatbelts use isn't required for adults in the back seat in some U.S. states(even though it should be).
They've been the law here for 30 years.
blkhawk1 year ago
Windshields are laminated to protect occupants of a car during an accident. There is more information on How Stuff Works.
verence1 year ago
Windscreen are laminated because
a) they are very likely hit by stones or debris that somehow gets in the way of your car and should not 'spiderweb' as this would be unsafe due to the reduced view and expensive as the windscreen would have to be replaced (and some of them are 1500$ and up, ouch...)
b) they are part of the static design of the passenger safety cell. So they have to withstand some torsion forces that would shatter tempered glass.

A laminated glass will have a small spiderweb if it really should get a heavy impact by a big stone, but the other parts stay (somehow) intact. If the impact is on the passenger side, you should be able to see enough to stop the car safely. If the impact is on the driver side ... well, you would probably too shocked to do anything reasonable or be able to lean over to the passengers side.

Why not all glass is laminated? Well that stuff is strong, but heavy and expensive. And, with tempered sides, a quick hit will break the glass to give access from a rescue team to reach inside or a passenger to crawl outside. Armoured cars have all side laminated glass, but with more than two layers.

If you really get outside a car in a crash, you're an idiot for not wearing a seatbelt. Why do some people think it would be safer outside? First you go through the windscreen and then there is all the debris from the crash, including your own car, ready to roll over you!

Anyway, the shards from the laminated glass are still glued to the glass, not able to give you deep dangerous cuts.

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